Radiochemical sterilization (RC-S) was first disclosed by this inventor in U.S. Pat. No. 5,422,068 and frequently described as the first novel approach to medical device sterilization since the early use of chemical sterilization in the presence of formaldehyde or ethylene oxide (Et-O) and high-energy radiation in the presence of gamma radiation or electron beam. It provides the medical device industry with a unique, hybrid process encompassing the attributes of chemical and radiation sterilization (RS) without the drawbacks associated with the use of the parent processes. Limitations on use of the most commonly used methods (namely, traditional RS and Et-O) have grown in the past three decades because of (1) degradation or undesirable changes in the properties of certain polymeric devices, such as those made from absorbable polyesters and polypropylene, caused by gamma radiation; (2) ineffective sterilization of simple and complex devices with Et-O and associated device recalls; and (3) toxic and explosive nature of Et-O. In contrast, the RC-S method combines the attributes of chemical sterilants and high-energy radiation and it entails (1) terminal sterilization of devices in a hermetically sealed package; (2) use of precisely generated formaldehyde through controlled radiolytic (caused by controlling the mass of the formaldehyde precursor and radiation dose) degradation of a solid polyformaldehyde insert to achieve surface sterility; and (3) less than 40% of the traditional radiation dose can be used to achieve surface and bulk device sterility—the radiation penetrates the mass of the device to ensure bulk sterility while complementing the formaldehyde in securing surface sterility. The commercial application of RC-S to segments of the medical device industry based on absorbable polyesters will represent a major milestone in such a fast-growing field encompassing traditional and new surgical products and innovative constructs for tissue engineering. A logical extension of the RC-S application will be for polypropylene-based devices, such as sutures, syringes, and many types of diagnostic devices.
The first commercial application of this technology will be radiation sterilization of absorbable polymeric devices. The use of RC-S is expected to extend to (1) other radiation-sensitive, biostable devices, such as those made of polypropylene (e.g., sutures and syringes); and (2) multicomponent packages, including resterilizable surgical kits containing both absorbable and non-absorbable components. However, U.S. Pat. No. 5,422,068 failed to address certain package-related requirements for the successful commercial use of the RC-S technology, which include (1) using a specially prepackaged, solid polymeric precursor that allows maximum diffusion of the generated formaldehyde into the gaseous environment without hindering its fugacity; (2) using a specially designed device holder for insuring the free diffusion of the generated formaldehyde from its precursor to effectively interact with any microflora on the medical device surface; and (3) providing a mechanism for practically irreversible, gradual immobilization of the residual formaldehyde in the package shortly after inactivating any microflora about the device. And this provided the incentive to explore the use of the package components subject of this invention that permit meeting the three requirements noted above.